A common acne pill taken by thousands of young British women is under investigation following safety concerns.

After it was recently linked to four deaths, regulators in France are suspending sales of the hormone treatment Dianette, which is also used as an oral contraceptive and is known to increase the risk of blood clots. In Canada, 11 deaths have been linked to the drug.

The European Medicines Agency, which regulates medicines across Europe, announced last week it will now carry out a review into its safety.

In the UK, concerns about the drug were raised following the recent deaths of several young women, among them Shannon Deakin in 2011.

The 16-year-old from Hoyland, South Yorkshire, had been prescribed Dianette by her GP for acne and had been taking it for around four weeks before she died from an undiagnosed deep vein thrombosis, when a blood clot from her leg travelled to her lungs.

Dianette — or Diane-35 as it’s known in France — is prescribed to more than 62,000 British women a year, usually for polycystic ovary syndrome (PCOS), a hormonal problem affecting young women which leads to multiple small ovarian cysts, irregular periods, acne and excess facial hair.

The condition is caused by an imbalance of the male sex hormone testosterone, which women also produce (it’s thought to help muscle strength and contribute to sex drive).

Some one in ten women are affected. Typically, it starts after puberty and can last for years.

‘Being overweight increases the chance of getting PCOS, but many women who develop it are fit and well,’ says Dr David Price, a consultant endocrinologist at the Morriston Hospital, Swansea.

In Shannon's case, a locum GP put the swelling and redness in her left thigh and 'knife-like' pains down to an infection

‘I tend to see 17 and 18-year-old girls who have had problems for a couple of years, although it can affect women until their 30s.

‘It can be very depressing for them. Some girls have so much facial hair as a result of the condition that they have to shave.

'Initially, we suggest losing weight or cosmetic treatments, but if they don’t work, then Dianette is often prescribed.’

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Dianette is a combination of two drugs — cyproterone (a form of the female hormone progesterone) and ethinylestradiol (an oestrogen), which effectively suppress the effect of testosterone.

As progesterone prevents ovulation, Dianette also works as an effective contraceptive.

'When you prescribe Dianette, you explain to patients there is an increased risk of blood clots, although the risk remains low'

DR DAVID PRICE

While other oral contraceptives carry a small increased risk of blood clots — which can be dangerous and potentially fatal if they travel to the lungs or brain — the type of progesterone in Dianette means the drug has one of the highest risks of blood clots of all oral contraceptives.

Cyproterone is 65 per cent more likely to cause a blood clot than levonorgestrel (a type of progesterone found in older oral contraceptive pills), according to a review of 25 studies published last year in the European Journal of Contraception And Reproductive Health Care.

Dr Price explains: ‘When you prescribe Dianette, you explain to patients there is an increased risk of blood clots, although the risk remains low.

'If you just wanted an oral contraceptive pill, you would go for a different drug which is slightly safer.

‘However, for women with PCOS, Dianette can really help.’

Made by the German pharmaceutical company Bayer, Dianette has been available in the UK since 1987, but is only licensed as a treatment for severe acne and excess facial hair. It’s normally taken for three or four months until the skin clears.

A spokeswoman for Bayer says: ‘Although Dianette also acts as an oral contraceptive, it should not be used solely for contraception, but reserved for those women requiring treatment for the androgen-dependent conditions.’

Dianette - or Diane-35 as it's known in France - is prescribed to more than 62,000 British women a year, usually for polycystic ovary syndrome (PCOS)

The French medicines agency last month revealed Dianette is widely used as a contraceptive in France. It is not clear what the situation is in the UK.

The risk of a blood clot while taking Dianette is, however, small.

Around 40 of every 100,000 women on it develop a blood clot in one year, compared with between five and ten women in 100,000 who are not taking the drug, according to the Medicines & Healthcare Products Regulatory Agency (MHRA).

But the Dianette risk is still lower than the risk of a blood clot during pregnancy (about 60 cases for every 100,000 pregnant women).

Professor Ellis Downes, a consultant gynaecologist at the Portland Hospital in London, says: ‘For those with acne and symptoms of PCOS, Dianette is a very good medication and I have been prescribing it for 20 years.

'Generally, it is a safe drug and the chance of developing a blood clot is very small.’

The warning signs of a blood clot include pain, swelling and tenderness in the leg, and warm and red skin — but many patients and doctors are still unaware of the symptoms, according to Lifeblood, the thrombosis charity.

In Shannon Deakin’s case, a locum GP put the swelling and redness in her left thigh and ‘knife-like’ pains down to an infection. She was prescribed antibiotics and anti-inflammatory drugs, but died 12 hours later.

An inquest heard the GP should have examined her calves, where swelling is a tell-tale sign of a blood clot.

However, as blood clots are ‘extremely rare’ at her age, there was no family history and she’d only been on the pill for a brief period, the GP’s actions were deemed ‘reasonable’.

The MHRA maintains the drug is safe. ‘Despite recent developments in France, we have no new concerns and there is no need for a woman who is feeling well to stop taking her medicine.

‘If women have any concerns about their treatment, they should contact their doctor.’